The invention relates to a method for removing particulate matter from a gaseous stream. More specifically, it is directed to removing submicron particulates from a gaseous stream by nucleation.
The removal of contaminant particles from gaseous streams is accomplished in different ways such as by chemical reaction or physical separation. The latter methods include cyclone separators; fabric filters, such as baghouses; electrostatic precipitators; adsorption on solid surfaces; and "washing".
These methods are generally commercially suitable for the removal of larger particulate sizes but are less effective for capturing or removing submicron particulates.
In order to remove submicron particulates, various methods employing venturi scrubbers have been suggested; see for example, U.S. Pat. Nos. 4,141,701; 3,894,851; and 3,883,327. In the removal of particulates with venturi scrubbers, the particulate-laden gas is accelerated to high velocity in a venturi while water is injected through spray nozzles located in or adjacent the throat portion of the venturi. Nucleation such as described in U.S. Pat. No. 4,049,399 is a low energy process for removal of submicron particulates where the particulates function as the nucleating agents for condensation of water vapor. Generally, the prior art accomplishes this heterogeneous nucleation where the population density of the water molecules in the gas phase is adequate to develop the nucleation or condensation phenomenon. Alternatively, it is also enhanced by cooling the gas such that there is greater condensation occurring on the submicron particulates.
The present invention is directed to a method to enhance the nucleation process by increasing the water content of the gas above "saturation" conditions with isothermal operation and with minimum consumption of energy. Thus, the "efficiency" of nucleation is increased.